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Study of heavy-flavor quarks produced in association with top-quark pairs at √s =7 TeV using the ATLAS detector

Aad, G. and Abajyan, T. and Abbott, B. and Abdallah, J. and Abdel, Khalek S. and Abdelalim, A. A. and Abdinov, O. and Aben, R. and Abi, B. and Abolins, M. and Abouzeid, O. S. and Abramowicz, H. and Abreu, H. and Abulaiti, Y. and Acharya, B. S. and Adamczyk, L. and Adams, D. L. and Addy, T. N. and Adelman, J. and Adomeit, S. and Adye, T. and Aefsky, S. and Aguilar-Saavedra, J. A. and Agustoni, M. and Ahlen, S. P. and Ahles, F. and Ahmad, A. and Ahsan, M. and Aielli, G. and Åkesson, T. P. A. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2014) Study of heavy-flavor quarks produced in association with top-quark pairs at √s =7 TeV using the ATLAS detector. PHYSICAL REVIEW D, 89 (7). ISSN 2470-0010

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Abstract

Using a sample of dilepton top-quark pair (t ¯t) candidate events, a study is performed of the production of top-quark pairs together with heavy-flavor (HF) quarks, t ¯t + b + X or t ¯t + c + X, collectively referred to as t ¯t + HF. The dataset used corresponds to an integrated luminosity of 4.7 fb−1 of proton–proton collisions at a center- of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The presence of additional HF quarks in the t ¯t sample is inferred by looking for events with at least three b-tagged jets, where two are attributed to the b-quarks from the t ¯t decays and the third to additional HF production. The dominant background to t ¯t + HF in this sample is t ¯t + jet events in which a light-flavor jet is misidentified as a heavy- flavor jet. To determine the heavy- and light-flavor content of the additional b-tagged jets, a fit to the vertex mass distribution of b-tagged jets in the sample is performed. The result of the fit shows that 79 ± 14 (stat.) ± 22 (syst.) of the 105 selected extra b-tagged jets originate from HF quarks, three standard deviations away from the hypothesis of zero t ¯t + HF production. The result for extra HF production is quoted as a ratio (RHF) of the cross section for t ¯t + HF production to the cross section for t ¯t production with at least one additional jet. Both cross sections are measured in a fiducial kinematic region within the ATLAS acceptance. RHF is measured to be [6.2 ± 1.1(stat.) ± 1.8(syst.)]% for jets with pT > 25 GeV and | η| < 2.5, in agreement with the expectations from Monte Carlo generators.

Item Type: Article
Subjects: Q Science / természettudomány > QC Physics / fizika
SWORD Depositor: MTMT SWORD
Depositing User: MTMT SWORD
Date Deposited: 05 Mar 2024 07:06
Last Modified: 05 Mar 2024 07:06
URI: https://real.mtak.hu/id/eprint/189643

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